Doug — the notification will be because I explicitly @mention ‘d you in the reply.

Yes, the behaviour of these forums is not a good advert for BuddyPress — although some of that is down to the coding of this site, rather than a BuddyPress specific problem.

Recently, a plugin version of bbPress was released, which significantly improved support for forums on a BuddyPress based site. That gives proper notifications, and the sort of features you’d expect from regular forums. Unfortunately, the alternative ‘group based forums’ as used on this site, really don’t deliver a good experience.